Bottom filling adhesive for packaging large-size chip, preparation method of bottom filling adhesive and packaging structure

Abstract

The invention discloses an underfill adhesive for packaging a large-size chip, a preparation method of the underfill adhesive and a packaging structure, and the underfill adhesive comprises the following raw materials in parts by mass: 53-65 parts of an inorganic filler, 22-28 parts of epoxy resin, 11-15 parts of a curing agent, 1-3 parts of an epoxy reactive diluent, 0.2-0.4 part of a dispersant, 0.1-0.3 part of a silane coupling agent and 0.2-0.4 part of an accelerant. Wherein the epoxy resin comprises nano silicon dioxide filled bisphenol A epoxy resin and methyl phenyl polysiloxane resin. The underfill adhesive provided by the invention has excellent fluidity and flexibility, low thermal shrinkage and water absorption, and high adhesive force and reliability, and is suitable for underfill of chips, especially large-size chips; in addition, the packaging structure using the underfill adhesive for underfilling also solves the problem that different material interfaces of the packaging structure are easy to layer.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of chip packaging, and particularly relates to a bottom filling adhesive for large-size chip packaging, a preparation method thereof and a packaging structure. BACKGROUND

[0002] One application of the bottom filling adhesive can be found in Figure 1 : the bottom filling adhesive is filled between the bottom of a chip 1 and a substrate 2, and a bottom filling adhesive layer 3 is formed after being heated and solidified. The solder joint 4 is a connecting point formed by connecting the chip 1 and the substrate 2. Large-size chips (such as 300mm wafers, 450mm wafers, Chiplets in advanced packaging, 3DIC, etc.) are the core direction to promote the development of the semiconductor industry towards high performance and high integration. The gap between the large-size chip and the substrate is narrower, and the flow path of the bottom filling adhesive is longer during bottom filling, so the bottom filling adhesive needs to have the characteristics of low viscosity and fast flow. Delamination is prone to occur at the interface between the large-size chip, the bottom filling adhesive layer and the substrate in a humid heat environment, so the bottom filling adhesive needs to have the characteristics of high toughness, high adhesion and high reliability. However, the current bottom filling adhesive is not suitable for the bottom filling of large-size chips. SUMMARY

[0003] Therefore, the purpose of the present application is to provide a bottom filling adhesive for large-size chip packaging, a preparation method thereof and a packaging structure.

[0004] To achieve this purpose, the following technical solutions are adopted in the present application: In a first aspect, the present application provides a bottom filling adhesive for large-size chip packaging, comprising the following raw materials in mass fraction: inorganic filler 53-65 parts, epoxy resin 22-28 parts, curing agent 11-15 parts, epoxy active diluent 1-3 parts, dispersant 0.2-0.4 parts, silane coupling agent 0.1-0.3 parts, and accelerator 0.2-0.4 parts; wherein the epoxy resin comprises nano-silica filled bisphenol A type epoxy resin and methylphenyl polysiloxane resin.

[0005] In the bottom filling adhesive of the present application, the inorganic filler is mainly used to reduce the thermal expansion coefficient of the cured product of the bottom filling adhesive; the epoxy resin is used as the resin matrix, mainly to provide the adhesion and mechanical properties of the bottom filling adhesive; the accelerator and the curing agent are selected from conventional accelerators and curing agents compatible with the epoxy resin, and the curing agent reacts with the epoxy resin to form a cured product with a three-dimensional network structure under a certain temperature; the accelerator is used to accelerate the crosslinking reaction and improve the reaction efficiency; the epoxy active diluent is used to reduce the viscosity of the bottom filling adhesive; the dispersant is used to reduce or even avoid the agglomeration of the inorganic filler through steric hindrance effect; and the silane coupling agent is used to improve the adhesion and reliability between the bottom filling adhesive and the substrate and the chip.

[0006] Optionally, the inorganic filler is in a mass fraction of 53-65 parts, 55-58 parts, 55-63 parts, or 58-63 parts.

[0007] Optionally, the epoxy resin is in a mass fraction of 22-28 parts, 22-26 parts, or 26-28 parts.

[0008] Optionally, the mass ratio of the nanosilica filled bisphenol A type epoxy resin and the methylphenyl polysiloxane resin in the epoxy resin is 1: (0.3-0.35), 1: (0.3-0.5), 1: (0.3-0.6), 1: (0.3-1.8), 1: (0.3-1.9), 1: (0.3-2), 1: (0.3-3), 1: (0.35-0.5), 1: (0.35-0.6), 1: (0.35-1.8), 1: (0.35-1.9), 1: (0.35-2), 1: (0.35-3), 1: (0.5-0.6), 1: (0.5-1.8), 1: (0.5-1.9), 1: (0.5-2), 1: (0.5-3), 1: (0.6-1.8), 1: (0.6-1.9), 1: (0.6-2), 1: (0.6-3), 1: (1.8-1.9), 1: (1.8-2), 1: (1.8-3), 1: (1.9-2), 1: (1.9-3), or 1: (2-3).

[0009] Optionally, the curing agent is in a mass fraction of 11-15 parts, 11-12 parts, 11-13 parts, 11-14 parts, 12-13 parts, 12-14 parts, or 13-14 parts.

[0010] Optionally, the dispersant is in a mass fraction of 0.2-0.4 parts or 0.2-0.3 parts.

[0011] Optionally, the inorganic filler is silica with a particle size of no more than 3 μm.

[0012] Optionally, the curing agent is an amine curing agent, such as a diethyl toluene diamine curing agent or a DMDC curing agent.

[0013] Optionally, the epoxy resin active diluent is a bifunctional diluent, such as XY622.

[0014] Optionally, the silane coupling agent is KBM-603 or KH540.

[0015] Optionally, the accelerator is a tertiary amine accelerator or an imidazole accelerator, such as a DMP-30 accelerator or a 2-ethyl-4-methyl imidazole accelerator.

[0016] Optionally, the underfill adhesive further comprises a trace dye, such as 0.1-0.2 parts of a dye.

[0017] In a second aspect, the application provides a preparation method of the underfill adhesive, comprising: taking each raw material by mass fraction and mixing, dispersing and vacuum defoaming the mixed adhesive, and obtaining the underfill adhesive.

[0018] In a third aspect, the application provides a packaging structure, which can refer to Figure 1 comprising a chip 1, a substrate 2, and an underfill adhesive layer 3 filled between the bottom of the chip 1 and the substrate 2; the underfill adhesive layer 3 is the underfill adhesive described above.

[0019] Optionally, the chip is a large-size chip.

[0020] Compared with the prior art, the application has the following advantages and beneficial effects: 1. The underfill adhesive of the application has the characteristics of rapid flow, and also has high toughness, high adhesion and high reliability, and is suitable for underfilling of chips, especially large-size chips; 2. The packaging structure using the underfill adhesive of the application to perform underfilling solves the problem of easy delamination between different material interfaces of the packaging structure. BRIEF DESCRIPTION OF DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiment or prior art description. Obviously, the drawings in the following description are only some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative labor.

[0022] Figure 1 The packaging structure shown in the embodiment of the application is a schematic diagram; Figure 2 The cross-sectional photo of the packaging structure using the underfill adhesive of Example 1 is shown; Figure 3 The cross-sectional photo of the packaging structure using the underfill adhesive of Comparative Example 2 is shown; The drawings show that: 1-chip, 2-substrate, 3-underfill adhesive layer, 4-welding point. DETAILED DESCRIPTION

[0023] The technical solutions of the application will be described in detail below with reference to the embodiments of the application. Obviously, the described embodiments are only some of the embodiments of the application, not all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the application.

[0024] To further illustrate the present application, the following examples and comparative examples are described in detail below. The raw materials used in the following examples and comparative examples are all commercially available and are as follows: Inorganic filler: commercially available silica, D100 particle size < 3 μm; Epoxy resin: nano-silica filled bisphenol A type epoxy resin, brand: NANOPOX® E 500, room temperature viscosity 20 Pas, epoxy equivalent weight 275 g / eq; methyl phenyl polysiloxane resin, brand: SH-3048, room temperature viscosity 80-500 cPs; Curing agent: DMDC curing agent, ingredients: 3,3-dimethyl-4,4-diamino dicyclohexyl methane; Epoxy reactive diluent: XY622, ingredients: 1,4-butanediol diglycidyl ether; Silane coupling agent: KBM-603, ingredients: N-β- (aminoethyl) -γ-aminopropyl trimethoxysilane; KH540, ingredients: 3-aminopropyl trimethoxysilane; Promoter: DMP-30, ingredients: 2,4,6-tris (dimethylaminomethyl) phenol; 2-ethyl-4-methyl imidazole promoter; Dispersant: brand: ANJEKA-6042A, a hyperbranched polyester compound containing imino group anchor functional groups; brand: ANJEKA-6860, a copolymer solution containing acidic groups; Dyeing agent: carbon black. The raw materials and the weight parts of each raw material used in the bottom filling glue of Examples 1-6 and Comparative Examples 1-4 of the present application are shown in Table 1. It should be noted that the mass ratio in Table 1 refers to the mass ratio of nano-silica filled bisphenol A type epoxy resin and methyl phenyl polysiloxane resin.

[0025] Table 1 Raw materials and weight parts of each raw material used in the bottom filling glue of examples and comparative examples The bottom filling glue of the examples and comparative examples uses the same preparation process, and the specific steps are as follows: (1) The raw materials are weighed and added to the stirring cup of the centrifugal mixer, and then preliminary stirring and mixing are carried out; the stirring parameters are set as follows: 1100 r / min for rotation, 1500 r / min for revolution, and 100 s for stirring time; (2) The preliminary mixed glue is added to the three-roll cylinder for dispersion treatment, and the inlet gap and outlet gap of the three-roll cylinder are set as 25 μm and 10 μm, respectively; (3) Vacuum defoaming is carried out using a centrifugal mixer; the vacuum defoaming parameters are set as follows: 1100 r / min for rotation, 1500 r / min for revolution, and 90 s for vacuum defoaming time.

[0026] The underfill adhesive obtained from the above examples and comparative examples was subjected to performance tests, and the test methods were as follows: 1. Viscosity: determined by a digital rotary viscometer, test conditions: 14# rotor at 25℃, rotation speed 50r / min.

[0027] 2. Flowability: a silicon wafer with a copper column of size 15mmx25mm was placed on a PCB board and fixed, the PCB board was placed on an electric heating plate at a temperature of 110℃ and preheated for one minute, an adhesive dispenser was used to dispense 40-45mg of underfill adhesive along the long side of the silicon wafer, under the action of capillary force, the underfill adhesive would flow at the bottom of the silicon wafer, and the time for the silicon wafer to be filled was recorded, i.e. the flow time.

[0028] 3. High temperature tensile rate: the underfill adhesive was cured at 165℃ / 2h, and the cured product was prepared into a sample of size 12mmx3mmx(0.1-0.3)mm, the tensile rate of the sample was tested by DMA, and the test conditions were: in the Controlled Force mode, the force was increased to 18N at a speed of 5N / min, and the test temperature was 245℃.

[0029] 4. Coefficient of thermal expansion: reference standard ASTM E831-2019; the underfill adhesive was cured at 165℃ / 2h, and the cured product was prepared into a sample of size 5mmx5mmx2mm, the coefficient of thermal expansion of the sample was tested by TMA equipment; the test conditions were: preloading force 0.05N, first scanning: from room temperature to 260℃ at a heating rate of 10℃ / min, second scanning: from room temperature to 260℃ at a heating rate of 5℃ / min; the coefficient of thermal expansion was obtained from the second heating segment curve data, specifically, the coefficient of thermal expansion was the slope of the second heating segment curve.

[0030] 5. Water absorption rate: the underfill adhesive sample cured at 165℃ / 2h was placed in Uhast for 96 hours, and the water absorption rate of the sample was tested; the Uhast conditions were: temperature 130℃, relative humidity 85%RH.

[0031] 6. Reliability test: including testing the adhesion of the underfill adhesive to the silicon wafer before and after Uhast. The underfill adhesive was cast in a pudding mold with a diameter of 3 mm and a height of 2 mm, and the end of the cast underfill adhesive was in contact with the silicon wafer. The silicon wafer and the pudding mold were fixed, and the underfill adhesive was cured at 165℃ / 2h. Then the pudding mold was removed, and the cured sample was taken out. The adhesion of the cured sample to the silicon wafer was tested using a push force machine. The cured sample was placed in Uhast conditions for 192 hours, and the Uhast conditions were: temperature 130℃, relative humidity 85%RH. The cured sample was taken out, and the adhesion of the cured sample to the silicon wafer was tested using a push force machine. The adhesion was the adhesion after Uhast. During the test of the adhesion, the test speed of the push force machine was 50um / s, and the contact height was 20um.

[0032] 7. Layered observation: the underfill adhesive was filled between the chip and the substrate, and was heated and cured at 165℃ / 2h to obtain a packaging structure sample. The packaging structure sample was cut open, and the cross section was observed using SEM to see if there was delamination.

[0033] The test results are shown in Table 2 below. Please refer to Figures 2-3 , which shows the cross section photos of the packaging structures using the underfill adhesives of Example 1 and Comparative Example 2, respectively. It can be seen from the cross section photos that the packaging structure using the underfill adhesive of Example 1 has no delamination phenomenon, but the packaging structure using the underfill adhesive of Comparative Example 2 has delamination phenomenon at the interface between the underfill adhesive layer and the substrate.

[0034] The viscosity and flow time were used to characterize the flowability, the high temperature tensile rate was used to characterize the flexibility, the thermal expansion coefficient was used to characterize the thermal shrinkage performance, and the adhesion before and after Uhast was used to characterize the reliability. From the test data, it can be seen that: 1. The above Examples 2-4 and Comparative Examples 1-2 constitute a control test group. By comparing the test data of Examples 2-4 and Comparative Examples 1-2, it can be seen that compared with Comparative Examples 1-2, the flexibility of the underfill adhesive of Examples 2-4 is significantly improved, the thermal expansion coefficient and water absorption rate are significantly reduced, the adhesion and adhesion reliability are significantly enhanced, and the delamination problem between different material interfaces in the packaging structure is solved.

[0035] 2. The underfill adhesives of Comparative Examples 3-4 also include nano-silica filled bisphenol A type epoxy resin and methylphenyl polysiloxane resin, which can solve the delamination problem of the packaging structure, but the performance of the underfill adhesive is relatively poor due to the use of specific amounts of raw materials.

[0036] 3. The above properties of the underfill adhesive of Examples 1-7 are relatively good, and the delamination problem between different materials of the packaging structure is also solved, but it can still be seen that the amount ratio of the nano-silica filled bisphenol A type epoxy resin and the methyl phenyl polysiloxane resin has an influence on the properties of the underfill adhesive. When the mass ratio of the nano-silica filled bisphenol A type epoxy resin and the methyl phenyl polysiloxane resin is 1: (0.5-2), the underfill adhesive has relatively better comprehensive properties.

[0037] Table 2 Test data of the underfill adhesive of the examples and comparative examples Based on the above, in the material system of the underfill adhesive of the present application, when the epoxy resin comprises the nano-silica filled bisphenol A type epoxy resin and the methyl phenyl polysiloxane resin, the delamination problem of the packaging structure can be solved. When the raw materials are in specific amounts, the above properties of the underfill adhesive are relatively good. Further, when the mass ratio of the nano-silica filled bisphenol A type epoxy resin and the methyl phenyl polysiloxane resin is a specific mass ratio, the above properties of the underfill adhesive are further improved.

[0038] The inventors believe that the mechanism by which the above technical effects can be achieved is the synergy between the nano-silica filled bisphenol A type epoxy resin and the methyl phenyl polysiloxane resin. The methyl phenyl polysiloxane resin has a Si-O-Si bond as the main chain, and the Si-O-Si bond and the Si-O-C bond in the nano-silica filled bisphenol A type epoxy resin can be stably combined by bonding; the nano-silica in the nano-silica filled bisphenol A type epoxy resin is filled in the pores of the polymer chain, and when the methyl phenyl polysiloxane resin and the nano-silica filled bisphenol A type epoxy resin are compounded, the nano-silica rigid inorganic particles are dispersed in the epoxy resin crosslinked network after curing. The nano-silica filled bisphenol A type epoxy resin and the methyl phenyl polysiloxane resin synergize to obtain a more stably combined flexible crosslinked network, and at the same time, the nano-silica as a rigid inorganic particle is dispersed in the flexible crosslinked network, which can also physically inhibit the shrinkage of the flexible crosslinked network, thereby exhibiting high toughness, high adhesion, high reliability, low thermal expansion coefficient, low water absorption, and other characteristics in the macroscopic view.

[0039] Finally, it should be noted that the terms "comprising", "including", or any other variant thereof are intended to cover non-exclusive inclusions, so that processes, methods, articles, or devices that include a series of elements not only include those elements, but also include other elements not explicitly listed, or inherent to such processes, methods, articles, or devices.

[0040] While the preferred embodiments of the application have been described, additional variations and modifications can be made to these embodiments by those skilled in the art once they have the benefit of the present disclosure without departing from the spirit and scope of the application. Accordingly, it is intended that the appended claims include all such modifications and variations as fall within the scope of the present application.

[0041] It is apparent that those skilled in the art can make various changes and modifications to the application without departing from the spirit and scope of the application. It is therefore intended that the present application cover all such changes and modifications that are within its scope.

Claims

1. Underfill for large-size chip packaging, characterized by: The invention comprises the following raw materials in parts by mass: 53 to 65 parts of inorganic filler, 22 to 28 parts of epoxy resin, 11 to 15 parts of curing agent, 1 to 3 parts of epoxy reactive diluent, 0.2 to 0.4 parts of dispersant, 0.1 to 0.3 parts of silane coupling agent and 0.2 to 0.4 parts of accelerator; wherein the epoxy resin comprises nano-silica filled bisphenol A epoxy resin and methylphenyl polysiloxane resin.

2. The underfill for large-size chip packaging according to claim 1, wherein: The mass ratio of the nano-silica filled bisphenol A epoxy resin to the methylphenyl polysiloxane resin is 1:(0.3-3).

3. The underfill for large-size chip packaging according to claim 1, wherein: The mass ratio of the nano-silica filled bisphenol A epoxy resin to the methylphenyl polysiloxane resin is 1:(0.5-2).

4. The underfill for large-size chip packaging according to claim 1, wherein: It also includes 0.1 to 0.2 parts of a dye.

5. The underfill for large-size chip packaging according to claim 1, wherein: The inorganic filler is silicon dioxide.

6. The underfill for large-size chip packaging according to claim 1, wherein: The curing agent is an amine curing agent.

7. The underfill for large-size chip packaging according to claim 1, wherein: The epoxy reactive diluent is a difunctional diluent.

8. The underfill for large-size chip packaging according to claim 1, wherein: The accelerator is a tertiary amine accelerator or an imidazole accelerator.

9. The method for preparing an underfill for large-size chip packaging according to any one of claims 1 to 8, characterized in that: The raw materials are taken in parts by mass and mixed, and the mixed colloid is dispersed and vacuum degassed to obtain the bottom filling glue.

10. The packaging structure is characterized by: The invention comprises a chip, a substrate and an underfill glue layer filled between the bottom of the chip and the substrate; the underfill glue layer is the underfill glue according to any one of claims 1 to 8.

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